Thermoelectric devices and methods of manufacture

ABSTRACT

Thermoelectric devices are provided. In one embodiment, a thermoelectric device may include a glass wafer defined by conductive vias, a second wafer, and a plurality of metal film disposed between the glass wafer and the second wafer and against solid, conductive, integral, end surfaces of the conductive vias. A nanogap may be disposed between the metal film and the second wafer. The nanogap may have been created by applying a voltage extending between the conductive vias and the second wafer. Methods of forming the devices, along with methods of using the devices to transform heat energy to electricity, and for refrigeration, are also provided.

BACKGROUND OF THE INVENTION

A variety of thermoelectric devices, and methods of their manufactureand use, exist today for transforming heat energy to electricity, and/orfor cooling applications, such as solid state refrigerators. Many of theexisting thermoelectric devices, and methods of their manufacture anduse, experience one or more problems such as: having a complex,expensive, and/or timely manufacturing process; being inefficient; beinginconsistent, unreliable, and/or not durable; and/or experiencing one ormore other types of problems.

A thermoelectric device, and/or method of its manufacture and use, isneeded to decrease one or more problems associated with one or more ofthe existing thermoelectric devices and/or methods.

SUMMARY OF THE INVENTION

In one aspect of the invention, a device is provided comprising a glasswafer defined by at least one conductive via made of a second material,a second wafer, and at least one metal film disposed in-between theglass wafer and the second wafer. The at least one conductive viaextends through the glass wafer and ends at a solid, conductive,integral, end surface of the at least one conductive via. The metal filmis disposed against the solid, conductive, integral, end surface of theat least one conductive via. A nanogap is disposed in between the metalfilm and the second wafer. The nanogap was created by applying a voltageextending between the conductive via and the second wafer.

In another aspect of the invention, a method of forming a device isdisclosed. In one step, a glass wafer is provided which is defined by atleast one conductive via made of a second material. The at least oneconductive via extends through the glass wafer and ends at a solid,conductive, integral, end surface of the at least one conductive via. Inanother step, at least one metal film is disposed against the solid,conductive, integral, end surface of the at least one conductive via. Instill another step, the glass wafer is bonded to a second wafer so thatsaid at least one metal film is disposed between the glass wafer and thesecond wafer. In yet another step, a voltage is applied between the atleast one conductive via of the glass wafer and the second wafer, inorder to create a nanogap in between the metal film and the secondwafer.

In a further aspect of the invention, a method is disclosed of using adevice to at least one of provide electricity and to act as arefrigerator. In one step, a device is provided which comprises at leastone metal film disposed in-between a glass wafer and a second wafer. Themetal film is disposed against at least one solid, conductive, integralend surface of at least one conductive via defining the glass wafer. Ananogap is disposed in between the at least one metal film and thesecond wafer. The nanogap was created by applying a voltage between theat least one conductive via defining the glass wafer and the secondwafer. In another step, the device is used to at least one of transformheat energy to electricity and to act as a refrigerator by usingprovided electricity.

In yet another aspect of the invention, a device is provided comprisinga glass wafer defined by at least one conductive via made of a secondmaterial, a second wafer, and at least one metal film disposedin-between the glass wafer and the second wafer. The at least oneconductive via extends through the glass wafer and ends at a solid,conductive, integral, end surface of the at least one conductive via.The metal film is disposed against the solid, conductive, integral, endsurface of the at least one conductive via. A nanogap is disposed inbetween the metal film and the second wafer. The nanogap was created byapplying a voltage extending between the conductive via and the secondwafer.

These and other features, aspects and advantages of the invention willbecome better understood with reference to the following drawings,description and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a front-view of one embodiment of a thermoelectric device;

FIG. 2 shows a front-view of another embodiment of a thermoelectricdevice;

FIG. 3 shows a front-view of yet another embodiment of a thermoelectricdevice with electrical wires connected to the device;

FIG. 4 is a flowchart depicting one embodiment of a method of forming athermoelectric device; and

FIG. 5 is a flowchart depicting another embodiment of a method of usinga thermoelectric device.

DETAILED DESCRIPTION OF THE INVENTION

The following detailed description is of the best currently contemplatedmodes of carrying out the invention. The description is not to be takenin a limiting sense, but is made merely for the purpose of illustratingthe general principles of the invention, since the scope of theinvention is best defined by the appended claims.

FIG. 1 depicts one embodiment of a thermoelectric device 10, which maybe used for transforming heat energy to electricity, or may be used as arefrigerator for cooling by providing electricity to the device 10. Thedevice 10 may be used both as an energy conversion device, or as acooling device, such as a solid state refrigerator. As discussed morethoroughly below, the thermal conductivity of the thermoelectric device10 may be substantially lower than a device having a continuous thermalpath, while its electrical conductivity may remain substantially higher,thus allowing the device 10 to transform heat energy to electricity inan efficient manner. The thermoelectric device 10 may include a glasswafer 12 and a second wafer 14. The glass wafer 12 may be defined by aplurality of conductive vias 16 which are made of a second materialwhich is conductive, such as a metal material which is substantiallydoped, like doped silicon, a semi-metal, or other electrically andthermally conductive material. The conductive vias 16 are defined asconductive pathways. In other embodiments, any number of conductive vias16 may be used. The conductive vias 16 may be open at one end 18, mayextend through the glass wafer 12 along direction 20, may haveconductive side-walls 22 and 24, may end at solid, conductive, integral,end surfaces 26, and may be substantially doped in order to be veryconductive. In such manner, the conductive vias 16 may be integral,one-piece vias 16 extending through the glass wafer 12. The conductivevias 16 may be in a parallel array configuration as shown, with bucketor U-shaped vias, but in other embodiments, may be in any shape, size,or configuration.

The second wafer 14 may be identical to the glass wafer 12. In suchmanner, the second wafer 14 may be made of glass, and may have aplurality of conductive vias 17 extending through the second wafer 14 inthe same configuration as in the glass wafer 12. In one embodiment, therespective conductive vias 16 and 17 of both the glass wafer 12 and thesecond wafer 14 may both be made of silicon. In other embodiments, thesecond wafer 14 may differ from the glass wafer 12 in material, shape,size, configuration, type, and/or may have no conductive vias 17 or avarying number of conductive vias 17. For instance, in one embodiment,the second wafer 14 may be identical to the glass wafer 12 in shape, butmay have conductive vias 17 made of a different material, such as asemiconductor other than silicon or with different type of doping, thanthe conductive vias 16 of the glass wafer 12. In still anotherembodiment, a p-n junction may be formed between the conductive vias 17of the second wafer 14 and the conductive vias 16 of the glass wafer 12.In yet another embodiment, as shown in FIG. 2, the second wafer 114 of athermoelectric device 110 of another embodiment may comprise a solidsilicon wafer 114, without any conductive vias, while the glass wafer112 may be identical to the glass wafer 12 of FIG. 1 with conductivevias 116. A p-n junction may be formed between the conductive vias 116of the glass wafer 112 and the second wafer 114. In yet anotherembodiment, the second wafer 114 may comprise a semiconductor other thansilicon. In still another embodiment, the second wafer 114 may comprisea solid semiconductor wafer having different doping than the conductivevias 116 of the glass wafer 112.

As shown in FIG. 1, a plurality of metal film 28 may be disposedin-between the glass wafer 12 and the second wafer 14. Each metal film28 may be disposed against a corresponding solid, conductive, integral,end surface 26 of one of the conductive vias 16 of the glass wafer 12.In other embodiments, any number of metal film 28 may be used. In stillother embodiments, the device 10 may not have any metal film 28. Themetal film 28 may be thin, or in any shape, size, or configuration. Eachmetal film 28 may not completely cover each of the respective solid,conductive integral, end surfaces 26 of each of the respectiveconductive vias 16. For instance, each metal film 28 may cover aninternal portion 30 of each of the solid, conductive, integral, endsurfaces 26 of each of the conductive vias 16, but may not coverperimeters 32 of each of the conductive end surfaces 26. In otherembodiments, each metal film 28 may completely cover the perimeters 32of each of the conductive end surfaces 26, and/or be in different sizes,locations, and configurations. One or more nanogaps 42 may be disposedbetween the metal film 28 of the glass wafer 12 and the second wafer 14.The nanogaps 42 may comprise small, open gap areas of open space whichare substantially between 0-2 nanometers, and may have been created byapplying a voltage extending between the conductive vias 16 and thesecond wafer 14. The nanogaps 42 may help the device 10 have a lowerthermal conductivity while maintaining a much higher electricalconductivity by increasing the distance of the thermal path, and therebylowering the device's thermal conductivity. One or more troughs 34 maybe disposed to the sides 19 of the metal film 28 at the perimeters 32 ofeach of the end surfaces 26 in between the glass wafer 12 and the secondwafer 14. The troughs 34 may comprise small, open gap areas of openspace which are substantially between 0 to 150 nanometers. In otherembodiments, the troughs 34, nanogaps 42, glass wafer 12, second wafer14, metal film 28, and/or conductive vias 16 and 17 may be in varyingsizes, shapes, and configurations.

The glass wafer 12 and the second wafer 14 may be bonded together usingan anodical bonding process, a hydrophilic treatment, or another bondingprocess known in the art. The metal film 28 may be disposed between thebonded together glass wafer 12 and second wafer 14.

FIG. 3 shows another embodiment having the same thermoelectric device210 as in FIG. 1, with the exception that no nanogaps have been createdyet. Electrically-charged wires 236 may be attached to respectivemetalized back-sides 238 and 240 of the glass wafer 212 and second wafer214. By running electricity through the electrically charged wires 236of FIG. 3, one or more nanogaps 42 may be produced as shown in thedevice 10 of FIG. 1. The nanogaps 42 may be substantially between 0 to 2nanometers, and may be created between the metal film 28 of the glasswafer 12 and the adjacent surface 13 of the second wafer 14, which inthis embodiment is a portion of conductive via 17, but in otherembodiments, may be various portions of the second wafer 14. Thenanogaps 42 may help the device 10 have a substantially lower thermalconductivity than a continuous material, while maintaining a moderate tomuch higher electrical conductivity due to the presence of the vacuumnanogaps 42 between the hot and cold sides of the thermoelectric device10 and the ability of the electrons to tunnel through the vacuumnanogaps 42. This may allow the device 10 to transform heat energy toelectricity in a more efficient manner than current thermoelectricdevices.

FIG. 4 shows a flow-chart of one embodiment 350 of a method of forming adevice. In one step 352, a glass wafer may be provided. The glass wafermay be defined by one or more conductive vias made of a second material.The conductive vias may extend through the glass wafer, and may end atsolid, conductive, integral, end surfaces of the conductive vias. Inother embodiments of the method, the glass wafer and the conductive viasmay comprise any of their embodiments disclosed herein. The glass wafermay have been manufactured by patterning a silicon wafer, usingphotolithography and deep RIE, which may have resulted in a multitude ofsilicon needles protruding from the surface of the silicon substrate.This may have been followed by flowing wafer molten glass onto thesurface of the silicon wafer. The front and back surfaces of the formedwafer may have then been polished to form a glass wafer having solidsilicon vias embedded in it. A specified resistivity and size of thesilicon vias may have been obtained by pre-determining the silicon wafertype, shape, size, and/or material, along with the type, shape, size,material, and/or number of the needles, to obtain the results desired.

In another step 354, one or more metal films may be disposed against thesolid, conductive, integral, end surfaces of the conductive vias. Themetal film may comprise any of the metal film embodiments disclosedherein. In one embodiment, the metal films may be disposed so that theydo not completely cover the solid, conductive, integral, end surfaces ofthe conductive vias. In still another embodiment, the metal films may bedisposed so that they cover internal portions of the solid, conductive,integral, end surfaces of the conductive vias, but do not coverperimeters of these conductive end surfaces. In other embodiments, themetal film may be disposed in varying configurations.

In yet another step 356, the glass wafer may be bonded to a second waferwith the metal films disposed between the glass wafer and the secondwafer. The second wafer may comprise any of the second wafer embodimentsdisclosed herein. In one embodiment, during the bonding, at least onetrough, which may be between 0 to 150 nanometers, may be formed adjacentthe metal film in between the glass wafer and the second wafer. Thetrough may comprise an open gap. In another embodiment, the glass wafermay be bonded to the second wafer using at least one of anodicalbonding, hydrophilic treatments, or other bonding methods known in theart. In yet another step 358, a voltage may be applied between theconductive via of the glass wafer and the second wafer in order tocreate a nanogap, which may be between 0 to 2 nanometers, in between themetal film and the second wafer. This may be done by connectingelectrically charged wires to metalized back-sides of both the glasswafer and the second wafer, and running an electric charge through thewires.

FIG. 5 shows a flow-chart of one embodiment 460 of a method of using adevice to at least one of provide electricity and to act as arefrigerator. In one step 462, a thermoelectric device may be provided.The thermoelectric device may comprise at least one metal film disposedin-between a glass wafer and a second wafer. The metal film may bedisposed against at least one solid, conductive, integral end surface ofat least one conductive via defining the glass wafer. The metal film,glass wafer, second wafer, and conductive vias may comprise any of theembodiments disclosed herein. In one embodiment, the metal film may notcompletely cover the solid, conductive, integral, end surfaces of theconductive vias. In another embodiment, the metal film may coverinternal portions of the solid, conductive, integral, end surfaces ofthe conductive vias, but may not cover perimeters of these end surfaces.In still another embodiment, one or more nanogaps may be disposedadjacent a top surface of the metal film in between the glass wafer andthe second wafer. The nanogaps, may be substantially between 0 to 2nanometers, and may have been created by applying a voltage between theconductive via of the glass wafer and the second wafer. In yet anotherembodiment, one or more troughs, which may be substantially between 0 to150 nanometers, may be disposed adjacent the sides of the metal film inbetween the glass wafer and the second wafer.

In another step 464, the thermoelectric device may be used to at leastone of transform heat energy to electricity and to act as a refrigeratorby using provided electricity. The thermal conductivity of the devicemay be substantially lower than the electrical conductivity of thedevice. The transforming of heat energy to electricity may beaccomplished by heating one side of the device, which may causeelectrons to move from the hot side to the cold side of the devicetraversing the vacuum gap by tunneling, whereas the phonons (latticeheat vibrations) may not be capable of doing so because the nanogap maybe too large for them to overcome. This may result in allowing for themaintenance of a large temperature difference between the hot and coldsides of the device, thus increasing its efficiency. The use of thedevice as a refrigerator may be accomplished by applying electricity orcurrent to the device.

One or more embodiments of the invention may reduce one or more problemsassociated with one or more of the thermoelectric devices and/or methodsof the prior art. For instance, one or more embodiments of the inventionmay result in: a less complex, less expensive, and less timelymanufacturing process; a more efficient device which transforms moreheat into electricity, or provides a more efficient refrigerator; a moredurable, consistent, and reliable device; and/or may reduce one or moreother problems of one or more of the prior art devices and/or methods.

It should be understood, of course, that the foregoing relates toexemplary embodiments of the invention and that modifications may bemade without departing from the spirit and scope of the invention as setforth in the following claims.

1. A device comprising: a glass wafer defined by at least one conductivevia made of a second material, wherein said at least one conductive viaextends through said glass wafer and ends at a solid, conductive,integral, end surface of said at least one conductive via; a secondwafer; at least one metal film disposed in-between said glass wafer andsaid second wafer, and disposed against said solid, conductive,integral, end surface of said at least one conductive via; and a nanogapin between said metal film and said second wafer, wherein said nanogapwas created by applying a voltage extending between said conductive viaand said second wafer.
 2. The device of claim 1 wherein the device is athermoelectric device for transforming heat energy to electricity. 3.The device of claim 1 wherein the device is used as a refrigerator byproviding electricity to said device.
 4. The device of claim 1 whereinthe thermal conductivity of the device is substantially lower than theelectrical conductivity of the device due to the nanogap.
 5. The deviceof claim 1 wherein the second material is at least one of metal, andsemi-metal.
 6. The device of claim 1 wherein said glass wafer is definedby a plurality of conductive vias.
 7. The device of claim 6 wherein saidplurality of conductive vias are in a parallel array configuration. 8.The device of claim 1 wherein said second wafer is at least one of asolid silicon wafer and a semiconductor other than silicon.
 9. Thedevice of claim 1 wherein said second wafer is at least one of identicalto said glass wafer and identical to said glass wafer in shape withconductive vias made of a semiconductor other than silicon.
 10. Thedevice of claim 1 wherein said at least one metal film does notcompletely cover the solid, conductive, integral, end surface of said atleast one conductive via.
 11. The device of claim 10 wherein said atleast one metal film covers an internal portion of the solid,conductive, integral, end surface of said at least one conductive via,but does not cover a perimeter of said solid, conductive, integral, endsurface of said at least one conductive via.
 12. The device of claim 1wherein one or more troughs are disposed at one or more sides of said atleast one metal film in between said glass wafer and said second wafer.13. The device of claim 1 wherein said at least one conductive via issubstantially doped.
 14. The device of claim 1 wherein said glass waferand said second wafer are at least one of anodically bonded together andbonded together using hydrophilic treatments.
 15. The device of claim 1wherein said nanogap is substantially between 0 to 2 nanometers.
 16. Thedevice of claim 12 wherein said one or more troughs are substantiallybetween 0 to 150 nanometers.
 17. A method of forming a devicecomprising: providing a glass wafer defined by at least one conductivevia made of a second material, wherein said at least one conductive viaextends through said glass wafer and ends at a solid, conductive,integral, end surface of said at least one conductive via; disposing atleast one metal film against said solid, conductive, integral, endsurface of said at least one conductive via; bonding said glass wafer toa second wafer so that said at least one metal film is disposed betweensaid glass wafer and said second wafer; and applying a voltage betweensaid at least one conductive via of said glass wafer and said secondwafer in order to create a nanogap in between said metal film and saidsecond wafer.
 18. The method of claim 17 wherein the disposing stepcomprises disposing said at least one metal film against said solid,conductive, integral, end surface of said at least one conductive via sothat said metal film does not completely cover the solid, conductive,integral, end surface of said at least one conductive via.
 19. Themethod of claim 17 wherein the disposing step comprises disposing saidat least one metal film against said solid, conductive, integral, endsurface of said at least one conductive via so that said metal filmcovers an internal portion of the solid, conductive, integral, endsurface of said at least one conductive via, but does not cover aperimeter of said solid, conductive, integral, end surface of said atleast one conductive via.
 20. The method of claim 17 wherein the bondingstep comprises forming at least one trough adjacent said at least onemetal film in between said glass wafer and said second wafer.
 21. Themethod of claim 17 wherein the bonding step comprises bonding said glasswafer to said second wafer using at least one of anodical bonding andhydrophilic treatments.
 22. The method of claim 17 wherein the step ofapplying a voltage comprises attaching electrically charged wires tometalized back-sides of the glass wafer and the second wafer.
 23. Themethod of claim 17 wherein the nanogap is substantially between 0 to 2nanometers.
 24. The method of claim 20 wherein said at least one troughis substantially between 0 to 150 nanometers.
 25. A method of using adevice to at least one of provide electricity and to act as arefrigerator: providing a device comprising: at least one metal filmdisposed in-between a glass wafer and a second wafer, and disposedagainst at least one solid, conductive, integral end surface of at leastone conductive via defining said glass wafer, wherein a nanogap is inbetween said at least one metal film and said second wafer, said nanogaphaving been created by applying a voltage between said at least oneconductive via defining said glass wafer and said second wafer; andusing said device to at least one of transform heat energy toelectricity and to act as a refrigerator by using provided electricity.26. The method of claim 25 wherein said at least one metal film does notcompletely cover the solid, conductive, integral, end surface of said atleast one conductive via.
 27. The method of claim 25 wherein said atleast one metal film covers an internal portion of the solid,conductive, integral, end surface of said at least one conductive via,but does not cover a perimeter of said solid, conductive, integral, endsurface of said at least one conductive via.
 28. The method of claim 25wherein said nanogap is substantially between 0 to 2 nanometers.
 29. Themethod of claim 25 wherein the thermal conductivity of the device issubstantially lower than the electrical conductivity of the device. 30.The method of claim 25 wherein one or more troughs are disposed adjacentsaid at least one metal film in between said glass wafer and said secondwafer.
 31. The method of claim 30 wherein said one or more troughs aresubstantially between 0 to 150 nanometers.
 32. A device comprising: aglass wafer defined by at least one conductive via made of a secondmaterial, wherein said at least one conductive via extends through saidglass wafer and ends at a solid, conductive, integral, end surface ofsaid at least one conductive via; a second wafer; and a nanogap betweensaid solid, conductive, integral, end surface of said at least oneconductive via of said glass wafer and said second wafer, wherein saidnanogap was created by applying a voltage extending between saidconductive via of said glass wafer and said second wafer.
 33. The deviceof claim 32 wherein said second wafer is a solid semiconductor waferhaving different doping than said at least one conductive via of saidglass wafer.
 34. The device of claim 32 wherein said second wafer issubstantially identical to the glass wafer, but has conductive vias witha different type of doping than the conductive vias of the glass wafer.35. The device of claim 34 wherein a p-n junction is formed between theconductive vias of the second wafer and the conductive vias of the glasswafer.
 36. The device of claim 33 wherein a p-n junction is formedbetween the conductive via of said glass wafer and the second wafer. 37.The device of claim 34 wherein the conductive vias of both the secondwafer and the glass wafer are silicone.